In recent years, portable devices have become markedly sophisticated. The power supplies for such portable devices are desired to be small and have a high capacity. However, the smaller the size, the more difficult it is to produce batteries with a high capacity. To overcome this difficulty, development is underway on tube-shaped wound batteries used as the power supplies for portable devices. For example, an advantage of cylindrical batteries over prismatic batteries is that it is easy to increase the capacity and to reduce the size of the batteries.
Patent Literature 1 teaches a battery including a cylindrical bottomed metallic case with a small diameter and a sealing member that seals the open end of the case. The metallic case accommodates a wound electrode assembly. The electrode assembly includes first and second electrodes, a first current collector lead connected to the first electrode, and a second current collector lead connected to the second electrode. In a usual wound electrode assembly, two current collector leads extend in opposite directions with one of the leads being welded to the bottom of the metallic case. In Patent Literature 1, however, both the first current collector lead and the second current collector lead are directed toward the open end of the metallic case because the fact that the diameter of the metallic case is small makes it difficult to weld the current collector lead to the bottom of the metallic case.